The overall objective of this proposal is to elucidate the etiologic relationship between childhood exposure to Chinese salted fish and the development of nasopharyngeal carcinoma (NPC) as suggested by epidemiologic and animal data. A case-control study of NPC in the Chiu Chau and Hakka populations of southern China is proposed. The goals are as follows: (1) to establish that early exposure to Chinese salted fish is a major risk factor for NPC among these intermediate risk populations and that their lower risk relative to the Cantonese is a result of their lower level of exposure, (2) to better quantity of usual consumption at various time periods, (3) to examine whether exposure to salted fish past early childhood is associated with an increased risk of NPC, and (4) to examine the interaction, if any, between intake of salted fish and dietary micronutrients such as vitamins C and A in the pathogenesis of NPC. In Shantou Prefecture (population is Chiu Chau), mothers of about 300 young (under age 40 years) NPC cases and mothers of an equal number of age and sex matched controls will be interviewed regarding the childhood environment of study subjects. In Meixian Prefecture (population is Hakka), mothers of about 200 young (under age 40 years) NPC cases and mothers of three times as many age and sex matched controls will be similarly interviewed. Chinese salted fish has been shown to cause mutation in bacteria (S. typhimurium) and morphological transformation in mammalian cells (C3H10T1/2 mouse embryo cells). It is proposed that these two bioassays be employed to guide the isolation and characterization of the carcinogenic compound(s) contained in Chinese salted fish. Ultimately, chronic whole animal experiments using highly purified or synthetic material will be conducted to confirm the carcinogenicity of suspected compounds.